At least 15 people have been killed and 10 severely burnt in Andhra Pradesh after an explosion at a gas pipeline belonging to the state-owned Gas Authority of India Limited (GAIL) caused a massive fire.

The blast took place at 5:30 am due to a gas leak in the pipeline at Nagaram in the East Godavari District, around 560 km from Hyderabad. Several people were burnt alive in the fire that followed, its flames shooting up almost 20 metres along with thick smoke.

District Collector Neetu Kumari Prasad said the number of dead could rise.

It took over two hours to bring the fire under control. The gas supply line has been cut off.

The incident took place at a site near a refinery complex of the state-owned Oil and Natural Gas Commission, which has now shut its gasfield.

The Centre and Andhra Pradesh governments have both ordered investigations.

GAIL chairman BC Tripathi said the fire broke out in an 18-inch pipeline. "The reasons for the accident are not known yet. We are currently focused on rescue and relief operations," he said.

Prime Minister Narendra Modi expressed condolences and said he had spoken to GAIL authorities and asked them to ensure relief at the accident site.

GAIL is the country's largest state-owned natural gas processing and distribution company.